The invention relates generally to expandable fasteners. In particular, it relates to a fastener suitable for connecting a plurality of panels where part of the fastener will engage one of the panels along an inaccessible side, and the fastener must therefore be capable of being locked into place from the accessible side.
Prior art devices have been proposed, but have several disadvantages. Typical fasteners are shown in U.S. Pat. No. 3,651,734 issued to McSherry on Mar. 28, 1972. Most of the McSherry fasteners are relatively inconvenient to use requiring that a tool be inserted through a hole in the one-piece fastener head to move the arms into an over-center position whereby a portion of each arm contacts one side of the panel to secure the fastener in a panel opening. Those fasteners not requiring an insertable tool to expand the panel-engaging arms either require a nut and bolt means or on an integral pivot pin and plunger. Rotation of the bolt is a time-consuming task, and usually a tool is required to turn it. The plunger-actuatable fastener is more easily used, but is not a one-piece fastener, and further has a smooth, non-serrated shaft which does not engage the head of the fastener to prevent collapse of the arms of the fastener in place. Instead, as in the other fasteners of McSherry, the collapse of the panel-engaging arms is prevented only by forces created by the flexing of what are typically called toggle members or arms, and flexible members. Similarly, the plunger-actuatable fastener is non-permanently engaged to the panel opening, the head of the plunger being in non-flush engagement with the head of the fastener and permitting the plunger to be grasped and pulled axially and away from the head to cause collapse of the arms and permit removal of the fastener. The non-flush fit of the plunger head relative to the fastener head is also undesirable with respect to appearance and utility.